Biomedical Engineering Reference
In-Depth Information
Fig. 6.13
Biologically
induced interface
A causes a function of cell B due to cell-cell interaction on the gate sensing surface.
In this chapter, vascular endothelial cell and tumor cell correspond to cell A and B,
respectively, for example. The noninvasive real-time measurement of the invasion
of cancer cells to the vascular endothelial cell layer and basement membranes was
performed using vascular endothelial cell-based field-effect transistor (VEC-FET),
which is based on potentiometric detection of molecular recognition on the gate
insulator. The shift of the V
T
caused by the charge density change on the gate
insulator can be monitored during the invasion process of tumor cells. The negative
shift of the V
T
has been successfully detected around 4 h after addition of invasive
tumor cells (HeLa cells). This result indicates that positive change of charge density
was induced on the surface of the gate insulator as a result of degradation of a
negative-charged basement membrane on the gate insulator by secretion of enzyme
from tumor cells. The platform based on the VEC-FET is suitable for a real-time
and simple invasion assay system.
6.4
Molecular Recognition Based on Intrinsic Molecular
Charges
6.4.1
Genetic Analysis
6.4.1.1
Detection of DNA Molecular Recognition Events
The principle of genetic FET is based on the detection of charge density change
on the gate surface which is induced by the specific binding of DNA molecules
[
9
-
17
]. Oligonucleotide probes are immobilized on the surface of the gate insulator.
The genetic FET is immersed in a measurement solution together with an Ag/AgCl
reference electrode with saturated KCl solution. The potential of a measurement
solution is controlled and fixed by the gate voltage (V
G
) through the reference
electrode. When complementary DNA molecules are contained in a sample solution,
hybridization occurs at the surface of the gate area. Since DNA molecules are
negatively charged in an aqueous solution, a hybridization event can be detected
